DOOM Effect
by Ordinarycomet3
Summary: Doomguy(2016 Doomguy) ends up in the Mass Effect universe and finds himself right in the middle of the Reaper invasion. So what does he do? Why, RIP AND TEAR, UNTIL IT IS DONE! (M cause violence, death, gore and fuck awesomeness)


**Greetings and welcome to my story. I came up with the idea for this story after having finished DOOM, and I wondered 'what would happen if this death machine of a man was placed in the war against the reapers?'.**

 **Well, this story is my answer to that question. NOTE: This story will have a great emphasis on the Doomguy (which is what I'm mainly calling him) and the excessive amounts of RIP AND TEAR that he does. So if you're looking for a deep, moving story-line about the Doomguy, sorry but I don't have one. Also WARNING: THIS CONTAINS SPOLIERS FOR THE END OF DOOM, SO DON'T READ IT IF YOU HAVEN'T FINISHED THE GAME YET.**

 **Anyway, warning, there will be gore (obviously) and a whole ton of badassery, and I won't be providing real, rational, scientifically sound reasons for why Doomguy can do what he does (carry around an arsenal powerful enough to face down hell itself, gain the power to punch barons of hell to death etc.) cause I feel like that would just detract from the fun of Doomguy killing shit.**

 **The story will basically just be ME3 but with Doomguy in it, doing his thing. So... yeah. Not sure what else to say. I'm just doing this as a pilot, just to see what people think. If people like it, well I'll write more.**

 **I hope you enjoy.**

 **Disclaimer: I do not own Mass Effect or DOOM. All rights go to their respective owners.**

* * *

Blue electricity crackled along the mans green suit, primarily gathering at his the other two times he'd returned from hell, he was kept suspended in the air. He lifted his head to look into the steamy, dark room he was in. A lone figure walked towards him.

"You've won-it's over." The figure said in a harsh, robotic voice. "You stopped the invasion and closed the portal." The figure got closer, revealing it to be a three foot tall robot with thin arms and legs, it's head had a vertical blue line down the middle. It's whole body was smooth, and it's hands bore four fingers. This was Samuel Hayden, head of the UAC. "But it's come at a price - Argent, VEGA. This entire operation." He stopped in front of the man, who was known as the Doomslayer, or just Doomguy.

"You see, I've watched you work, come to understand your motivation." Hayden took a step back. "You think the only way is to kill them all-leave nothing behind-and you may be right. But we can't just shut it all down! Without Argent energy it will be worse." Hayden shook his head. "I don't expect you to agree."

The man held his arm out, and pulled a demonic looking object from Doomguy. It bore similarities to the grip of a blade, but appeared to have a skull-like object on the bottom which had red energy surging around it. "But with this we can continue our work!" Hayden said, lifting the crucible into the air. He turned to look at Doomguy.

"I am not the villain in this story." The cyborg said, walking back and forth. "I do what I do, because there is no other choice."

 _"Re-routing tether co-ordinates... Complete."_ A synthesised female voice droned

"Our time is up." Hayden said. "I can't kill you, but I won't have you standing in our way." Suddenly a massive red blade burst forth from the crucible, strange inscriptions present on the length of it.

"Until we see each other again." Hayden said darkly, and turned to walk off. As he did so, the tether system installed in Doomguy's suit activated, and he vanished in a burst of blue light.

* * *

 ***2186 CE, Martian surface, outside Prothean archives***

Doomguy's vision cleared and he felt himself hit solid, barren, red ground. He sprung to his feet and looked around, quickly realising he was still on Mars. However, he could instantly tell he wasn't on the Mars he had just been on, the large unfamiliar building to his left with its markings and design didn't remotely resemble a UAC facility. He was on top of a small cliff which overlooked the facility.

He looked over the edge, immediately noticing the group of soldiers in large, bulky white armour. The next thing he noticed was that there were two people in much thinner, blue armour kneeling on the ground with their hands bound behind their backs. Before Doomguy could do anything, the soldiers in white armour executed the ones in blue armour by shooting them in the back of their heads.

One of the soldiers exploded into bloody chunks two seconds later, coating anything in the vicinity with his blood.

"What the hell!?" One of them said. He was clearly the commander, his armour looked more advanced and more intimidating than the rest.

"We're under fire!" Another said, before he too exploded into red chunks and a spray of blood when a high powered gauss round impacted his torso and tore through his armour, shredding him to pieces. A muffled thump sounded to their right and the remaining soldiers spun around, weapons raised. For a moment, all of them were confused when they saw a man in unfamiliar green armour charging towards them with what looked like a shotgun in his hands at impossibly high speeds. The closest soldier to the new attacker couldn't even pull the trigger on his gun before his head was obliterated by a close quarters shotgun blast.

"Open fire!" The squad leader ordered. The muzzles of the remaining 4 soldiers burst into life, hurtling mass effect propelled rounds at their attacker, who didn't even flinch when the rounds struck his armour and did nothing more than ping off his near impenetrable suit as he raked his shotgun and fired into the chest of another soldier. Dazed, the man stumbled back, only to suddenly feel a knee slamming into his chest but before he could scream Doomguy punched him in the head with enough force to crush both his helmet and skull, instantly killing him. The green armoured man didn't miss a beat, his shotgun was already out before the dead soldier had hit the floor.

Raking his shotgun, Doomguy activated the special modification on his gun, an explosive shotgun blast. He pulled the trigger, launching the projectile towards two of the soldiers who had grouped together. The round struck home, instantly turning the first one into a mess of bloody chunks whilst severely dazing the other one and coating him in his friends blood and internal organs. Bolting forward, Doomguy reached the soldier and swept his feet out from under him. Before the soldier could process anything the Doom marine punched him in the torso with enough strength to obliterate it, causing his lifeless legs and head to flop to the ground, spraying blood onto the martian surface along with several chunks of flesh and organs.

Now only the squad leader was left. Much to the mans confusion and horror, Doomguy put his shotgun away and instead pulled out what appeared to be and very well was a chainsaw. Despite the Centurion's advanced training and mental conditioning, thanks to Cerberus, he couldn't help but let fear take hold of him as Doomguy charged towards him, revving his chainsaw. He hoped that his kinetic barriers, something he had that his troops didn't, would save him as he fired in vain at his charging opponent.

Unfortunately, Kinetic barriers are designed to stop bullets, not chainsaws.

When the green armoured man reached the Centurion, he swung the chainsaw in a diagonal arc, and it connected with the Cerberus soldier's right shoulder. Revving to max, Doomguy promptly sawed the man diagonally in half, his chainsaw easily carving through both armour, bone and flesh, making blood spray everywhere. When he was done, Doomguy took a step back as the Centurion's lifeless body fell and landed with a sickening slop on the ground, staining the martian surface with more blood.

The Doom slayer crouched next to the Centurion's severed upper body and reached out and tore the front of the troopers helmet off. For three seconds he stared at the dead man's face, which had a strange blue substance running in vein like patterns across it, his eyes an eerie blue. Doomguy stood up and then curb stomped the Centurion with enough force to crush the dead man's head.

In a blur of movement, Doomguy spun around and raised his Heavy Assault rifle. The first thing he noticed about the person he was aiming at was the gun in their hand, which Doomguy assumed was an assault rifle. The second thing he noticed was that they were wearing completely different armour, which was darker, much less bulky, and bore a red stripe down the right arm and on top of its helmet. The two aimed at each other for several tense seconds until the black armoured soldier spoke.

"Who are you? Identify yourself." They ordered, their voice identifying them as male. Doomguy said nothing, but lowered his weapon slightly. His instincts told him he could trust this stranger, and that they weren't going to try and kill him. The armoured man glanced to the left before looking back at the Doom marine. "Did you kill those soldiers?" He asked, referring to the Cerberus troopers. Doomguy inclined his head slightly in the positive.

"Identify yourself." The man asked again. Two more similarly armed soldiers walked up next to him, one wearing a massive suit of armour, the other wearing a blueish suit of armour and who was clearly female. Doomguy, yet again, didn't reply. Instead he lowered his weapon even further, to indicate that he didn't mean them harm.

"Shepard, why is Cerberus here?" The woman asked, suspicion in her tone. Commander John Shepard glanced to his left.

"Ash, how would I know?" He said before looking back at Doomguy. For a few seconds he studied the armoured man before he lowered his gun. "Are you an Alliance marine?" He asked, although he highly doubted it. Doomguy shook his head briefly. After a few moments of quick thinking, plus another glance at the dead Cerberus troopers, Shepard made a decision.

"I don't know who you are, where you're from, or how you got here but right now none of that matters. If you're against Cerberus that's good enough for me." Shepard removed one hand from his assault rifle and extended it towards Doomguy.

"Shepard, you can't just trust him!" Ashley Williams snapped, still looking at Doomguy with suspicion. "He could be a Cerberus assassin for all we know!"

"Then why would he attack a squad of Cerberus troops?" Shepard shot back, his dark eyes narrowing behind his visor. "We're wasting time arguing about it. If he was an assassin, he'd have already tried to kill us." Shepard looked back at Doomguy. "Will you help us fight Cerberus?" He asked plainly. Doomguy looked down at Shepard's hand and then back up at the Commander's helmet.

He reached out and shook the commanders hand.

* * *

 **So kinda short but I just wanted to get Shepard and Doomguy to meet, and to get Doomguy to hate Cerberus. I assure you, there will be a greater amount of RIP AND TEAR in the next chapter. Also Doomguy has ALL his weapons, I'm not even gonna bother trying to explain how he can actually carry them all at once. So please drop a review telling me what you thought and I'll (hopefully) see you in the next chapter!**

 **RIP AND TEAR, UNTIL IT IS DONE!**


End file.
